1. Field of the Invention:
This invention relates to a film data reading device for a camera.
2. Description of the Prior Art:
There has been proposed during recent years a film cartridge 2 which is provided, on the peripheral surface thereof, with a film data code part 1 indicative of the sensitivity or the number of frames of the film contained in the cartridge, as shown in FIG. 1 of the accompanying drawings. The film data code part 1 consists of an electric conductive part 1a and a non-conductive part 1b. These parts are combined into varied patterns which indicate the information on the film. For reading the film data or information from the cartridge 2, a plurality of contact pieces are arranged on the side of a camera to come into contact with the data code part 1 of the film cartridge 2, and the electric conductive state of the data code part 1 is detected. FIG. 2 shows an example of this reading arrangement. In this case, holes 4a are formed in the frame wall 4 of the camera body in positions corresponding to the data code part 1 of the cartidge 2. Contact pieces S are arranged to protrude thrugh the holes 4a into a cartidge (loading) chamber 5. When the chamber 5 is loaded with the cartridge 2, the film data provided on the cartridge 2, is read out by means of these contact pieces S. One end of each contact piece S is inserted into a holding member 6 which is secured to the frame 4 of the camera body. Further, there are two different types of the cartridge 2. In one type, the diameter d of the middle cylindrical part 2b having the data code part 1 is arranged to be smaller than the diameter D of each of the cap parts 2a of the cartridge (D &gt;d). In the other type, the diameter d is arranged to be about equal to the diameter D (D .apprxeq.d).
In the case of the reading device of the prior art described, the position of the cartridge 2 within the cartridge chamber 5 is determined by the diameter D, which is standardized. Whereas the dimension of the other diameter d has not been clearly standardized. In view of this, the protruding extent of the contact pieces S into the cartridge chamber 5 has been arranged to be sufficient for absorbing variations in the diameter d. Therefore, in the event of a camera which is incapable of retracting a film rewinding fork from the cartridge chamber 5, the cartridge 2 must be inserted into the cartridge chamber 5 in a scooping manner by tilting it. In that case, the contact pieces S are apt to be deformed or damaged while the data code part 1 is also apt to be damaged. Furthermore, the excessive protruding extent of the contact pieces S tends to cause them to catch the cap part 2a of the cartridge to deteriorate the operability of the camera. Even in the case of a camera which is arranged to have the film rewinding fork retractable from the cartridge chamber 5, inadvertent insertion of the cartridge into the cartridge chamber in a tilted posture by the operator or inadvertent contact of a finger of the operator with the contact pieces S likewise tends to deform or damage the contact pieces S.
To solve this problem, an improvement on the conventional film data reading device has been disclosed in Japanese Laid-Open Patent Application No. Sho 57-202524. According to that disclosed device, which is as shown in FIG. 4, a rotatable shaft 54 is constantly urged to turn counterclockwise by a spring which is not shown; a sensor lever 55 and contact pieces S1 to S6 are secured to the shaft 54; the contact pieces S1 to S6 are allowed to protrude into a cartridge chamber 56 when the sensor lever 55 senses that the chamber 56 is loaded with a film cartridge 2; and the film data is read out via these contact pieces. When the chamber 56 is not loaded with the cartridge 2, the sensing part 55a of the sensor lever 55 is left protrudent inside the cartridge chamber 56 through a hole 57a provided in the body frame 57 of a camera since the shaft 54 is under the counterclockwise urging force of the spring which is not shown. When the chamber 56 is loaded with cartridge 2, a front peripheral part of the cartridge 2 pushes the sensing part 55a in the direction of arrow A. This causes the shaft 54 to rotate clockwise against the urging force of the spring. Then, while the sensing part 55a is pushed out of the chamber 56, the contact pieces S1 to S6, which have stayed away from the inside of the cartridge chamber 56, protrude into the cartridge chamber 56 and thus come into contact with a film data code part 1 provided on the outside of the cartridge 2, so that the film data can be read out.
In accordance with the arrangement of the device disclosed, however, the cartridge loading force is utilized for obtaining a pushing force on the contact pieces S1 to S6. This arrangement necessitates an exertion of an unnecessary force in loading the chamber with the cartridge. This has thus been a hindrance to cartridge loading operation. Furthermore, even after the cartridge 2 has been placed in the chamber 56, the cartridge 2 is still receiving a force exerted in a direction in which it is to be taken out. This force drives the cartridge 2 out of the cartridge chamber 56 to a slight degree. Then, if the back lid of the camera is closed with the cartridge 2 in that incompletely loaded state, the film is apt to curl under that condition. Then, the curl either turns round the cartridge to cause inaccurate engagement of the tip of the film with a film guide groove or keeps the film in a twisted state. Therefore, the prior art device has been unsuited for a camera of the automatic film loading kind.